Transforming growth factor β plays an important role in enhancing wound healing by topical application of Povidone-iodine

Abstract

Povidone-iodine (PVI) is principally used as an antimicrobial agent. It has been found that 0.5% PVI can attenuate congestion, edema and pain induced by pressure sores. Thus this study aimed to assess the effects of 0.5% PVI on acute skin wounds. Four full-thickness excisional wounds were generated on the dorsal skin of male Sprague-Dawley rats with a 10-mm sterile punch. Two wounds were left untreated and the other two were dressed with gauze with 0.5% PVI for 1 hour per day for the first 5 days after injury. 10-mm full-thickness excisional wounds were also generated on the dorsal skin of rats treated with 10 mg/kg SB431542 and all wounds were treated with 0.5% PVI for 5 days. PVI treatment enhanced wound healing via promotion of expression of α SMA and TGF β, neovascularization and re-epithelialization. Interleukin 6 was reduced following PVI treatment. Inhibition of TGF β abolished the effect of PVI treatment on wound closure. These data show that topical application of 0.5% PVI could promote acute skin wound healing though increased expression of TGF β leading to enhanced formation of granulation tissue, even in the absence of obvious infection.

Figure 1

Povidone-iodine (PVI) treatment enhanced cutaneous wound closure and granulation tissue formation and maturation. (A) Representative photographs of wounds from a control and PVI treated rat. (B) Wound contraction (%) at day 1 to 14 post-injury. (C) Representative micrographs of H&E stained wound sections. Red arrows indicate red blood cells. Blue arrows indicate inflammatory cells. Grey arrows indicate fibroblasts. Red asterisks indicate new blood vessels. Scale bar = 50 μm. *p < 0.05, **p < 0.01 vs control. Data are means ± S.D, n = 12.

Figure 2

Povidone-iodine (PVI) treatment promoted alpha smooth muscle actin (α-SMA) expression. (A) Representative immunohistochemical α-SMA stained wound sections from a control and PVI treated rat. Scale bar = 50 μm. (B) Semi-quantitative analysis of α-SMA expression. (C) Representative western blotting for α-SMA in wound areas. (D) Semi-quantitative analysis of α-SMA expression, n = 4. *p < 0.05, **p < 0.01 vs control. Data are means ± S.D, n = 24.

Figure 3

Povidone-iodine (PVI) treatment promoted wound neovascularization. (A) Representative immunohistochemical CD34 stained wound sections from a control and PVI treated rat. Scale bar = 50 μm. (B) Semi-quantitative analysis of capillary density (/mm²). Capillary density was assessed by counting the number of CD34 positive microvessels in high-power fields (40x). *p < 0.05, **p < 0.01 vs control. Data are means ± S.D, n = 24.

Figure 4

Povidone-iodine (PVI) treatment increased transforming growth factor β expression. (A) Representative western blotting for transforming growth factor (TGF) β in wound areas. (B) Semi-quantitative analysis of TGF-β expression. *p < 0.05 vs control. Data are means ± S.D, n = 4.

Figure 5

The effect of povidone-iodine (PVI) treatment on macrophages. (A) Representative immunohistochemical CD68 stained wound sections. Scale bar = 50 μm. (B) Quantitative analysis of CD68+ cells (/high power fields). (C) Representative immunohistochemical inducible nitric oxide synthase (iNOS) stained wound sections. Scale bar = 50 μm. (D) Quantitative analysis of iNOS + cells (/high power fields). Data are means ± S.D, n = 24.

Figure 6

The effect of povidone-iodine (PVI) treatment on tumor necrosis factor (TNF) α and interleukin (IL) -6 expression at the wound site. (A) Representative immunohistochemical TNFα stained wound sections. Scale bar = 50 μm. (B) Semi-quantitative analysis of TNFα + cells (/high power fields). (C) Representative immunohistochemical IL-6 stained wound sections. Scale bar = 50 μm. (D) Semi-quantitative analysis of IL-6 expression. **p < 0.01 vs control. Data are means ± S.D, n = 24.

Figure 7

Povidone-iodine (PVI) treatment enhanced filaggrin expression. (A) Representative immunohistochemical filaggrin stained wound sections. Scale bar = 50 μm. (B) Semi-quantitative analysis of filaggrin expression. *p < 0.05 vs control. Data are means ± S.D, n = 24.

Figure 8

Inhibition of transforming growth factor β prevented the promotion of skin wound healing by Povidone-iodine (PVI) treatment. (A) Representative photographs of wounds from rats treated with inhibitor of transform growth factor β (SB431542) or vehicle and PVI. (B) Wound contraction (%) at day 1 to 11 post-injury. *p < 0.05, **p < 0.01 vs control. Data are means ± S.D, n = 12.